Homework _6 Solutions Final - ChemE 178: Homework #6...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: ChemE 178: Homework #6 Solutions 1.) Polymer blends are to be made from a poly(ethylenepropylene) (h-PEP) of weight average molecular weight Mw = 175,000, Mw/Mn=1.01 and a perdeuterated- poly(ethylenepropylene) (d-PEP), Mw=200,000, Mw/Mn=1.01. The d-PEP is the same in all respect as the h-PEP except that the d-PEP has all hydrogens exchanged for deuterium. The Flory parameter for the d-PEP/h-PEP pair is given by = (0.571/T)-6.6x10-4 , where T is the absolute temperature (K). Compute and plot the following: _______________________________________________________________________ _ A.) The normalized free energy of mixing G mix /Mk B T versus d-PB at the following temperatures: 300K, 350K, 385K and 450K. Use a spreadsheet program like Excel or a plotting program with computational capability to produce these plots. Use scales so that important details are visible. Begin with the Flory-Huggins Equation: ( 29 ( 29 ln ln A B A B A B B A B G Mk T N N = + + To get N A and N B , you will need to use the number average molecular weight. d-PEP: 200,000 198,020 1.01 w n M M PDI = = = h-PEP: 175,000 173,267 1.01 w n M M PDI = = = Assuming that the h-PEP and d-PEP have similar monomeric volumes, the segment lengths are simply the degree of polymerization. Note: This is not always the case. 173,267 2,475 70 198,020 2,475 80 h PEP A d PEP B N N N N-- = = = = = = The polymer blend is incompressible, so 1 A B = + Given the expression for , you can use the Flory-Huggins equation to plot the normalized free energy as a function of volume fraction. Gibbs Energy of Mixing-1.40E-04-1.20E-04-1.00E-04-8.00E-05-6.00E-05-4.00E-05-2.00E-05 0.00E+00 2.00E-05 4.00E-05 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 (d-PB) G/MkT 300 K 350 K 385 K 450 K B.) Compute the binodal and spinodal 's as a function of temperature and use these to compute and plot the phase diagram for this system. The binodal is define as ( 29 ( 29 ( 29 1 2 1 1 ln 1 ln 1 1 2 A A mix mix A B A A A A B G G N N = = +- + +- The binodal is calculated using the condition that binodal point lies on the same...
View Full Document

This note was uploaded on 12/09/2011 for the course CHEM ENG 178 taught by Professor Segalman during the Fall '08 term at University of California, Berkeley.

Page1 / 10

Homework _6 Solutions Final - ChemE 178: Homework #6...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online